Process of chemically coating sheets of cellulose esters with metal



' Patented Man 17, 1925.

UNITE-D STATES mm 1mm 01' IB'IIBOURG,

PATENT OFFICE.

nocma OI CEKIIGAIaI-Y COATING SHEETS OI CELLULOSE ESTEQS MET AL.

5 useful Improvements in and Relating to a Process of Chemically Coating Sheets of Cellulose Esters with Metal, of which the following is as cification.

The applicatlon of metallic coatings to certain materials, such as for instance acetylcellulose, which in consequence of their great disruptive resistance and other strength are particularly suited as dielectric is meeting with all sorts of difliculties. The coatin ought to adhere ermanently to the materia and further it latter in such a manner, that the formation of any kind of air bubbles and also of a vacuum between the coating and insulating material is prevented.

The process or method accordin to the present invention fully satisfies t ese requirements. Sheets of cellulose-ester or of super-xanthogenates are chosen by way of example as t e insulating material in the method hereinafter described. Even only at a thickness of millimetre the said inting material has given very good results. 4

- First the cellulose-esters sheets are sli htly sapom'fied on the surface in an alka ine bath, preferably in a 2% bath of caustic potash or caustic soda.

A- split-up product of the cellulose and acetic'acid will be liberated b the saponification. After rinsing the s eets, preferably in running water, a metal-salt solution is applied to the saponified surfaces.

It has been discovered that the split-up product of the cellulose ester, remaining on the saponified surfaces of the sheets, acts as a reducing agent, and thus precipitates metal from the metal-salt solution.

as to be attached to the- Application Med January 11, 1988. Serial No. 612,083.

The metal adheres to the surface prepared by the alkaline bath and forms a continuous coating.

The adhesion of this metallic coating is furthered by subsequently drying the sheets at a temperature of about 100 to 150 C.

In place of the alkaline bath, for which also ammonia may be employed, an acid bath may be used.

However the results obtained with the latter are not quite sogood, as owing to the action of the acids the precipitated metal is again dissolved in part.

Particularly silver is very goqfi as metal deposit, but also copper and 0 er metals ma be employed.

claim 1. The described process of chemically coating sheets of cellulose-esters with metal, which consists in slightly saponifying the surfaces'of the sheets, rinsing them in water,

and then causing a metal-salt solution to act thereon, precipitating thereby reduced metal on. the sapon-ified surfaces.

2. The described process of chemically coating sheets of cellulose-esters with metal, which consists in saponifying the surfaces of the sheets in an alkaline bath, and, after rinsing them in water, causing a metal-salt solution to act on the sapomfied surfaces, thereby precipitating reduced metal onthe latter. I

3. The described process of chemically coating sheets of cellulose esters with metal, which consists in superficially saponifying the sheets, rinsing them in water, causing a metal-saltsolution to act on the saponified surfaces and finally drying the metal-coated sheets in a temperature of about 100 to 150 C. Y

In testimony whereof I afiix my signa- .ture.

EMJL PFIFFNER. 

